Sorry for my poor english.
I'm considering using AWS CloudFront and inquiring the pricing policy from https://aws.amazon.com/cloudfront/pricing/
Other sections are understandable for me, but I can't understand when the "Regional Data Transfer Out to Origin" cost is charged.
As I understood, a CDN only fetches data from origin server for caching and there is no need to transfer data out to origin server.
Which case a CDN sends data to origin server?
The Regional Data Transfer Out to Origin from Amazon CloudFront to Origin Server refers to using POST, PUT & etc. requests, where there is a request payload.
Data Transfer out of Amazon CloudFront to your origin server (e.g. for POST and PUT requests) will be billed at the “Regional Data Transfer Out to Origin” rates listed in the Regional Data Transfer Out to Origin (per GB) table.